Guidelines - US Robotics COURIER User Manual

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COURIER HIGH SPEED MODEMS
&13 Hewlett Packard-Host Mode. Applies only to modems
attached to an HP mainframe that uses the ENQ/ ACK
protocol. Use in ARQ mode only. See Appendix E.
&14 Hewlett Packard-Terminal Mode. Applies only to
modems attached to terminals in an HP system that uses
the ENQ/ ACK protocol. Use in ARQ mode only. See
Appendix E.
&15 This setting is designed to enable flow control on the
phone link when the connection is not under error
control. For this to work for you, the remote modem
must have &15 capability.
Guidelines
In ARQ mode, a Courier set to &15 operates the same as it
does when set to &12. It acts on your XON /XOFF com-
mands, but does not pass them to the remote system. The
error control protocol enables the modems to control the
flow of data on the phone link.
In non-ARQ mode, a Courier set to &15 operates as
though flow control were disabled (&IO): it does not look
for your typed XON/XOFF commands. However, it
looks for XON /XOFF characters
coming in over the phone
link. When the remote operator sends XON/XOFF com-
mands, the Courier either resumes or stops transmitting
data over the link and drops the characters from the data
stream.
If both modems are set to &15, operators at each end can
signal the remote modem to stop sending, thereby
controlling the data flow on the phone link and
preventing their own modem's buffer from overflowing.
At the DTE/DCE interfaces, the modems independently
control the flow of data through their Transmit Data (&H)
settings.
Use of software flow control may prove satisfactory if you're
only transferring text files. However, if you're transferring non-
text (binary) files, or using an Xmodem-type protocol, disable
flow control entirely (&R1, &IO). In addition, set the modem to
&BO and &NO, so that the DTE and link rates are equal.
Interface Controls 4-11